The Role of Pesticides in Parkinson’s Disease

In the original description of Parkinson’s disease by none other than Dr. James Parkinson himself, he described a characteristic feature of the disease: constipation, which may precede the diagnosis by many years. In fact, bowel movement frequency may be predictive. Men with less than one bowel movement a day were four times more like likely to develop Parkinson’s an average of 12 years later. This could be simply a really early symptom of the disease tied to decreased water intake, however. Many Parkinson’s patients report never really feeling very thirsty, and perhaps that led to the constipation. “Alternately, one may speculate that constipation also increases the risk of Parkinson’s disease as constipation results in a longer stay of the feces in the bowel and thus more absorption of neurotoxicants,” neurotoxins from the diet.

Two studies suggest an association between constipation and Parkinson’s, but, at the same time, 38 studies link the disease to pesticide exposure and by now more than 100 studies link pesticides to an increased risk of up to 80 percent.

Many of these studies are on occupational exposure, like that experienced by farmworkers, who may reduce their risk of Parkinson’s by wearing gloves and washing their clothes, but Parkinson’s has also been linked to ambient exposure. In the United States where approximately a billion pounds of pesticides are applied annually, just living or working in high-spray areas may increase Parkinson’s risk. It’s the same with using pesticides in the home. I didn’t realize how common household pesticide use was, and a study out of UCLA suggests it might not be such a good idea. 

Pesticides may cause DNA mutations that increase susceptibility for Parkinson’s or play a more direct role. Many neurodegenerative diseases appear to be caused by the buildup of misfolded proteins. In Alzheimer’s, it’s the protein amyloid beta; in Creutzfeldt-Jakob and mad cow disease, it’s prions; in Huntington’s, it’s a different protein; and in Parkinson’s disease, it’s a protein called alpha synuclein. A variety of pesticides—8 out of the 12 tested by researchers—were able to trigger synuclein accumulation in human nerve cells, at least in a petri dish, though the study has since been retracted so it’s unclear what the data actually showed.

The buildup of synuclein may play a role in killing off specialized nerve cells in the brain, 70 percent of which may be gone by the time the first symptoms arise. Pesticides are so good at killing these neurons that researchers use them to try to recreate Parkinson’s disease in animals. Is there any way to stop the process? As of this writing, there aren’t yet any drugs that can prevent this protein aggregation. What about flavonoid phytonutrients, natural compounds found in certain fruits and vegetables? Flavonoids can cross the blood-brain barrier and may have neuroprotective effects, so researchers tested 48 different plant compounds to see if any could stop the clumping of synuclein proteins into the little fibers that clog up the cell. And, indeed, they found a variety of flavonoids that can not only inhibit the spider web-like formation of synuclein fibers, but some could even break them up. It turns out flavonoids may actually bind to synuclein proteins and stabilize them.

In my video Berries vs. Pesticides in Parkinson’s Disease, you can see healthy nerve cells and the neurites, the arms they use to communicate to one another. After exposure to a pesticide, however, you can see how the cell is damaged and the arms are retracted. But, if you first incubate the nerve cells with a blueberry extract, the nerve cell appears better able to withstand the pesticide effects. So, this implies that flavonoids in our diet may be combating Parkinson’s disease as we speak, and healthy diets may be effective in preventing and even treating the disorder. However, these were all petri dish experiments in a laboratory. Is there any evidence that people eating berries are protected from Parkinson’s?

A study published quite a long time ago suggested the consumption of blueberries and strawberries was protective, but it was a tiny study and its results were not statistically significant. Nevertheless, that was the best we had…until now. In a more recent study, those eating a variety of phytonutrients were less likely to develop Parkinson’s disease. Specifically, higher intake of berries was associated with significantly lower risk. The accompanying editorial, “An Apple a Day to Prevent Parkinson Disease,” concluded that more research is necessary, but, until then, “an apple a day might be a good idea.” Of course, that’s coming from a man. Apples appeared protective against Parkinson’s for men, but not women. However, everyone appeared to benefit from the berries.

We may not want to have our berries with cream, though, as milk may be contaminated with the same kind of neurotoxic pesticide residues found in the brains of Parkinson’s disease victims.


I’ve produced other videos on Parkinson’s disease, including: 

Learn about other neurological muscular disorders, including essential tremor and ALS:

The same reason Parkinson’s may be related to constipation may also explain the breast cancer connection. For more on this, see my video Breast Cancer and Constipation.

What else can berries do?

But what about all the sugar in fruit? See my videos If Fructose Is Bad, What About Fruit? and How Much Fruit Is Too Much?.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

How to Boost DNA Repair with Produce

“In the light of strikingly consistent observations from many epidemiological [population-based] studies, there can be little doubt that the habitual consumption of diets high in fruits and vegetables helps to reduce the risk of development of degenerative diseases, including many types of cancers.” Not satisfied with merely telling people to eat their fruits and veggies, scientists want to know the mechanism. I discuss this topic in my Which Fruits and Vegetables Boost DNA Repair? video.

Not just vehicles for antioxidants, fruits and vegetables contain innumerable phytonutrients that can boost our detoxification enzymes, modulate gene expression, and even modulate DNA repair pathways. “Until fairly recently…it was generally assumed that functions as important as DNA repair were unlikely to be readily affected by nutrition,” but, if you compare identical twins to fraternal twins, only about half to three quarters of DNA repair function is genetically determined. We may be able to control the rest.

“It is estimated that, on average, there are 800 incidents of DNA damage [in our bodies] per hour,” which is about 19,000 hits to our DNA every day. What’s more, “that DNA damage can cause mutations and give rise to cancer, if not repaired.” Thankfully, “the regulation of [DNA] repair can be added to the list of biological processes that are influenced by what we eat—and, specifically, that this might constitute part of the explanation for the cancer-preventive effects of many plant-based foods.”

Any plants in particular? Nine fruits and vegetables were tested to find out which ones were better able to boost DNA repair: lemons, persimmons, strawberries, oranges, choy sum (which is like skinny bok choy), broccoli, celery, lettuce, and apples. Which ones made the cut? Lemons, persimmons, strawberries, broccoli, celery, and apples all conferred DNA protection at very low doses.

Lemons, for example, were found to cut DNA damage by about a third. Was it the vitamin C? No. Removing the vitamin C from the lemon extract did not remove the protective effect. However, if you first boiled the lemon for 30 minutes, the protective effect was lost.


If it’s not the vitamin C, what might it be? That’s the subject of my video Citrus Peels and Cancer: Zest for Life?

Surprised that the lemon benefit was abolished by cooking? Find out which vegetables it may be best to eat raw in Best Cooking Method.

What about cooked versus raw garlic? See my video Inhibiting Platelet Activation with Garlic and Onions.

For more on DNA protection and repair, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

We Have Specific Fruit and Vegetable Receptors

According to a recent survey, the number of Americans adults who say they are eating ‘pretty much whatever they want’ is at an all-time high,” which unfortunately includes “too few fruits and vegetables,” as well as “too little variety.” Half of all fruit servings are taken up by just six foods: orange juice, bananas, apple juice, apples, grapes, and watermelons. Only five foods—iceberg lettuce, frozen potatoes, fresh potatoes, potato chips, and canned tomatoes—make up half of all vegetable servings. We’re not only eating too few fruits and veggies. We’re also missing out on the healthiest fruits, which are berries, and the healthiest vegetables, which are dark green leafies. The fruit and vegetable palette for our palate is sadly lacking.

Why does dietary diversity matter? As I discuss in my video Specific Receptors for Specific Fruits and Vegetables, different foods may affect different problems. Cabbage, cauliflower, broccoli, and Brussels sprouts are associated with lower risk of colon cancer in the middle and right side of our body, whereas risk of colon cancer further down on the left side of our body appears to be better lowered by carrots, pumpkins, and apples. So, “different F/V [fruits and vegetables] may confer different risks for cancer” of different parts of even the same organ.

Variety is the spice of life—and may prolong it. “Independent from quantity of consumption, variety in fruit and vegetable consumption may decrease lung cancer risk,” meaning if two people eat the same number of fruits and vegetables, the one eating a greater variety may be at lower risk.

It’s not just cancer risk. In a study of thousands of men and women, a greater quantity of vegetables and a greater variety may independently be beneficial for reducing the risk of type 2 diabetes. Even after removing the effects of quantity, “each different additional two item per week increase in variety of F&V [fruit and vegetable] intake was associated with an 8% reduction in the incidence of T2D [type 2 diabetes].” Why? Well, it “may be attributable to individual or combined effects of the many different bioactive phytochemicals contained in F&V. Thus, consumption of a wide variety of F&V will increase the likelihood of consuming” more of them.

“All the vegetables may offer protection…against chronic diseases,” but “[e]ach vegetable group contains a unique combination and amount of these [phytonutrients], which distinguishes them from other groups and vegetables within their own group.” Indeed, because “each vegetable contains a unique combination of phytonutriceuticals (vitamins, minerals, dietary fiber and phytochemicals), a great diversity of vegetables should be eaten…to get all the health benefits.”

Does it matter, though, if we get alpha-carotene or beta-carotene? Isn’t an antioxidant an antioxidant? No. “It has been shown that phytochemicals bind to specific receptors and proteins” in our bodies. For example, our body appears to have a green tea receptor—that is, a receptor for EGCG, which is a key component of green tea. There are binding proteins for the phytonutrients in grapes, onions, and capers. In my video The Broccoli Receptor: Our First Line of Defense, I talk about the broccoli receptor, for instance. Recently, a cell surface receptor was identified for a nutrient concentrated in apple peels. Importantly, these target proteins are considered indispensable for these plants foods to do what they do, but they can only do it if we actually eat them.

Just like it’s better to eat a whole orange than simply take a vitamin C pill, because, otherwise, we’d miss out on all the other wonderful things in oranges that aren’t in the pill, by just eating an apple, we’re also missing out on all the wonderful things in oranges. When it comes to the unique phytonutrient profile of each fruit and vegetable, it truly is like comparing apples to oranges.


This is one of the reasons I developed my Daily Dozen checklist of foods to incorporate into one’s routine. Download the free iPhone and Android apps, and be sure to watch my video Dr. Greger’s Daily Dozen Checklist.

I discuss how produce variety—not just quality and quantity—may be important in Apples and Oranges: Dietary Diversity and Garden Variety Anti-Inflammation, so I hope you’ll check them out. You can also learn more about why combining certain foods together may be more beneficial than eating them separately in Food Synergy.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: